591
FXUS10 KWNH 161845
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 PM EDT TUE JUN 16 2020
VALID JUN 16/1200 UTC THRU JUN 20/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SOUTHEAST U.S. CLOSED LOW AND COASTAL FRONT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
THE CUT-OFF UPPER LOW THAT IS CURRENTLY PARKED OVER SOUTH CAROLINA
IS EXPECTED TO REMAIN NEARLY STATIONARY THROUGH WEDNESDAY EVENING
BEFORE GRADUALLY LIFTING NORTH AND EVENTUALLY BECOMING ABSORBED BY
THE WESTERLIES BY THE WEEKEND. THIS IS SUPPORTING A SURFACE LOW
NEAR EASTERN NORTH CAROLINA THAT IS FUELING CONVECTION AND HEAVY
RAIN FOR PORTIONS OF THE SOUTHEAST AND MID-ATLANTIC REGION. THE
MODELS ARE INDICATING VERY GOOD SYNOPTIC SCALE AGREEMENT ON THE
PROGRESS OF THE UPPER LEVEL SYSTEM. AT THE SURFACE, THE 12Z NAM
IS SLIGHTLY WEAKER WITH THE LOW, BUT STILL WITHIN THE REALM OF
POSSIBILITIES. THEREFORE, A GENERAL MODEL BLEND WITH HIGH
CONFIDENCE CAN BE RECOMMENDED.
CLOSED LOW MOVING INTO THE NORTHWEST TUESDAY INTO THE NORTHERN
HIGH PLAINS BY THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 00Z FRIDAY, THEN 12Z
NAM/UKMET/ECMWF BLEND
CONFIDENCE: MODERATE
THE UPPER LEVEL LOW OVER WASHINGTON AND OREGON TUESDAY MORNING IS
FORECAST TO CROSS THE NORTHERN ROCKIES AND BECOME ABSORBED BY A
SECOND EVOLVING UPPER LOW OVER SOUTH-CENTRAL CANADA BY THURSDAY.
THIS WILL SUSTAIN AN OCCLUDED SURFACE LOW AND A SLOW MOVING COLD
FRONT ACROSS THE DAKOTAS THROUGH THE MIDDLE OF THE WEEK. THE TWO
MAIN DIFFERENCES NOTED IN THE GUIDANCE IS A STRONGER SYSTEM WITH
THE 12Z GFS ACROSS SASKATCHEWAN AND MANITOBA, AND THE 12Z CMC
BECOMES DISPLACED TO THE SOUTH OF THE MODEL CONSENSUS BY 00Z
FRIDAY, ALTHOUGH NOT TO THE SAME DEGREE AS THE 00Z CMC RUN.
THEREFORE A BLEND OF THE 12Z NAM/ECMWF/UKMET SHOULD SUFFICE AS A
STARTING POINT IN THE FORECAST PROCESS.
TROUGH APPROACHING THE PACIFIC NORTHWEST BY FRIDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/GEFS MEAN/00Z EC MEAN
CONFIDENCE: LIMITED-MODERATE
A SHORTWAVE TROUGH PIVOTING AROUND A BROAD UPPER LEVEL GYRE OVER
THE GULF OF ALASKA IS EXPECTED TO REACH THE OFFSHORE WATERS OF THE
PACIFIC NORTHWEST AND VANCOUVER ISLAND BY FRIDAY EVENING,
ACCOMPANIED BY A SLOW MOVING COLD FRONT. THE 12Z CMC IS FASTEST
IN BRINGING THIS TROUGH TOWARDS THE BRITISH COLUMBIA COAST, AND
THE NAM IS MORE AMPLIFIED BY 6Z FRIDAY AND CONTINUES THROUGH 00Z
SATURDAY. BY THE END OF THE FORECAST PERIOD FRIDAY EVENING, THE
GFS AND UKMET ARE BOTH INDICATING A BETTER DEFINED LOW PRESSURE
WAVE ON THE FRONT AFTER THE PRIMARY SURFACE LOW PASSES THROUGH.
FORECAST CONFIDENCE IS LIMITED BY THESE DIFFERENCES, AND THEREFORE
INCORPORATING SOME OF THE ENSEMBLE MEANS IS PRUDENT.
HAMRICK
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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